Exhaust gas cleaning systems disclosed in patent documents 1, 2 are known as a system for collecting particulate matter (hereinafter referred to as “PM”) included in an exhaust gas of a diesel engine to reduce the quantity of PM exhausted to the outside. This system includes a filter that is called a particulate filter (DPF: Diesel Particulate Filter). The filter is disposed in an exhaust system of an engine. This filter collects PM included in an exhaust gas so as to clean up the exhaust gas. In addition, the systems disclosed in the patent documents 1, 2 are configured to perform such control (manual regeneration control) that in order to prevent a filter from being clogged, start of the regeneration control is instructed by manual operation, and the temperature of an exhaust gas is then increased to burn off and remove PM deposited in the filter. Further, the system described in the patent document 2 is so configured that automatic regeneration control which automatically starts regeneration to burn off and remove deposited PM can also be performed.    Patent document 1: JP-A-2005-120895    Patent document 2: JP-A-2006-37925